Krissa Hjartar's varied sports interests have stimulated her to develop a fitness application, Starters, and videos with trainer Jason McClure that focus on circuit and interval training. Photos Provided to China Daily

Bogged down in the hectic life of a freelance designer in Shanghai, Krissa Hjartar missed having a regular workout routine. The Icelandic native was also apprehensive about outdoor exercise in the often-polluted environment of a big city.

Personal fitness and working out have always been a part of her life, Hjartar says. Growing up in town of just 1,200 people, she tried every sport available. It wasn't until she tried judo, though, that she had found her favorite. She went on to become a national champion in the sport from 1992 through 1999.

"I fell in love with it right away - and loved the fact that you use the opponent's force, weight and speed to your advantage," she says. Anyone, young or old, could train in judo. "Most importantly, it's a sport that requires constant learning," she says. "It's like chess, you are always learning a new game plan, but with your body."

After moving to China about two years ago, the former champion decided it was time to "restart" her career. She began sending workout videos that she created to friends who, like herself, were missing an active routine. Her friend Joe Luttwak, for example, had also gotten too busy to work out, and as a father of two he also began to experience back pain when he would lift, carry and play with his young children.

When he told Hjartar that his chronic back pain was beginning to subside after only two weeks of using her videos, she was convinced she could do more.

She set out to create what has quickly become a popular fitness application, Starters. It taps into one's existing network through Facebook, creating teams to help keep users motivated. The application offers a range of quick, fast-paced 10-minute workouts for users. Since she's not a certified personal trainer, Hjartar is featured as the trainee in most of the videos while the Starters trainer, Jason McClure, does the coaching.